Catalytic synthesis of organic compounds



T. B. HUDSON 2,664,433 CATALYTIC SYNTHESIS OF' ORGANIC COMPOUNDS 4 Sheets-Shea?l l Dec. 29, 1953 Filed May` 2o, 1949 Dec. 29, 1953 T. B. HUDSON 2,664,433

CATALYTIC SYNTHESIS OF ORGANIC COMPOUNDS Filed May 2o, 1949 4 sheets-sheet 2 EP3 AND PROPANE MAKE UP 53 EP3 AND PROPANE REFRIGERATION BFa PROPANE soLvEN-r 6, 60 48C 4 POLYMER B5 & som/ENT RECOVERY PROCESSES BUTENES soLvENT REACTION CHAMBER Dec. 29, 1953 T B, HUDSON 2,664,433

CATALYTIC SYNTHESIS 0F ORGANIC COMPOUNDS Filed May 20, 1949 4 Sheets-Sheet 5 REACT I VATOR CATALYST L l FT\ PRODUCTS \\\\\\V\vl loo T n Hz-coNTAlNING REACTIVATION GAS MAKE UP CATALYST INVEN TOR. T. B. HUDSON *EN BY A 7' TORNEVS Dec. 29, 1953 T. B. HUDSON CATALYTIC SYNTHESIS OF ORGANIC COMPOUNDS 4 heets-Sheet 4 Filed May 20, 1949 CATA LYST HYDRoGENv| REACTION M|XTURE INCLUDING ALCOHOLS JNVENTOR.

T. B. HUDSON //QC d M A 7' TOR/VE V5 provide improved methods usually involving complicated apparatus designs whereby indirect heat transfer is utilized in connection with portions oi catalytic materials so small as to allow su'icient heat to pass from or into the catalyst mass to accomplish the desired results. For example, particles of solid catalyst have been packed into relatively small tubes so that no portion of the catalyst is more than say one inch from a tube wall, and a number of such tubes connected in parallel, with a heat transfer medium being circulated about the exterior of the tubes. An alternative method has been to provide a system of coils or the like within a catalyst mass so that a heating or cooling medium, as required, may be circulated throughout the catalyst bed. Similar arrangements have been provided for reaction vessels employing moving catalysts. However, these methods have not been able to compensate fully for the low thermal conductivity of the usual catalysts. Furthermore, the surface of the tubes or other elements through which the heat transfer takes place, is at a temperature appreciably dif- .ferent from that generally prevailing in the reaction zone. This is disadvantageous, particularly with endothermic reactions where, in the case of hydrocarbon conversions for example, cracking, coke formation and other reactions take place on the superheated surfaces, which causes loss oi materials and fouling of equipment.

Other methods proposed for compensating for heat of reaction include superheating of reactants involved in endothermic processes above optimum temperatures, or the converse, that is insuicient preliminary heating of exothermic reactants. The inefficiencies of such methods are obvious. Catalyst poisoning may sometimes occur to an increased extent at either lowered or increased temperature.

Probably the most common method of bringing solid catalysts into contact with reactants is to place the catalyst in a reaction chamber, and pass the reactants therethrough at the desired ilow rate, temperature, and pressure. However, in many cases, it has been found useful to cause the solid catalyst particles to move through the reaction zone. Also in the case of gaseous or liquid catalysts, the catalyst is frequently passed through the reaction zone. Such catalyst, whether solid, liquid, or gaseous, which are passed through a reaction zone, are referred to herein as mobile or fluent catalysts. They may be passed either concurrently with or countercurrently to the reactants, depending upon the reactions being catalyzed, the catalyst, and other variables.

v It is an object of this invention to provide novel catalytic processes. Another object is to provide improved methods of operating catalytic systems,

particularly those employing mobile catalysts.

Another object is to enable a more delicate control of catalyzed organic reactions, particularly hydrocarbon conversion. A further object is to of contacting mobile catalysts with reactants. A further object is to provide for the control of catalyzed reactions with respect to temperature and/or products btained. Yet another object is to permit controlled variation in the quantity and/or activity of catalyst present at all points in a reaction zone. A still further object is to provide for the introduction of one or more catalysts into a reaction zone at a plurality of points. Another object is to provide for the concurrent or countercurrent iiow of catalyst thus introduced relative to the `iio'w of reactants. Another object is to correlate `oi turbulent ilow, static charges, etc.

the introduction of catalyst with certain reaction conditions in an exact manner so as to compensate, at least in part, for change in temperature and/or change in concentration of reactants or other reaction conditions. A further object is to provide for reactivating catalysts which have become deactivated in which processes so that the reactivated catalyst may be re-introduced into contact with reactants. Yet another object is to apply the principles of the invention as disclosed herein to the reaction of hydrogen with carbon oxides, particularly carbon monoxide, to form organic compounds including hydrocarbons and oxygenated derivatives thereof. A further object is to effect the reaction of hydrogen with carbon monoxide by means of a plurality of iuidized beds of powdered catalyst, the beds being maintained at different levels of activity by separate introduction thereinto of catalyst streams which have undergone reactivation to different extents. A still further object is to reactivate iron or other metallic synthesis catalyst in an improved manner by a process involving use of a plurality of fluidized beds maintained in a reactivation zone `with separate withdrawals of catalyst from each bed. Another object is to provide improvements in the formation of aldehydes, ketones, and/'or alcohols by reaction of carbon monoxide and hydrogen with olefins. Other objects and advantages of the invention will become apparent from the following disclosure.

My invention is essentially a method for carefully controlling catalytic processes by the multipoint addition of catalyst, specifically correlated with reaction conditions. Specific methods of operating are disclosed which are especially adapted for given types oi conversions. These diierent methods, while each employing the introduction of catalyst into a reaction zone at a plurality of points, are not at all to be considered as exact equivalents inasmuch as each is particularly designed to give optimum results for the given application, as will be more fully explained. I am aware that catalytic materials have occasionally in the past been described as being introduced into a reaction zone at more than one point. Such disclosures, however, have been vague, indefinite, and most unenlightening as to the purposes involved and exact results accom plished. I have found specific relationships between catalyst introduction and reaction conditions, and have devised novel methods of correlating the various factors involved whereby new and highly useful results are accomplished, as will be apparent from the detailed teachings hereinbelow set forth.

From one point of vieW, the invention may be considered as comprising three principal operational modifications. A rst modification has to do with catalysts which are miscible with one or more reactants, either by virtue of mutual solubility or because of small particle size of the catalyst allowing its suspension in reactants. Such a suspension may be in a more or less stable form, cr in a relatively separable form in which the catalyst is maintained in suspension by means Finely divided solid catalysts are frequently suspendved in gaseous reactants and passed through a zone maintained under desired reaction conditions. Such catalysts have been called fluid catalysts, which is in actuality a misnomer. However, they do often pass at the same rate of flow as the reactants and the entire mixture may be handled more or less as a single uid. As is accadde 'vvell known in the art,l the term "i'i'uidfwhen ap- -plied to powdered solid catalysts includes the susv- -pension of same in reactants under conditions'of vstraight-through now, 'in fluidized beds. fluid with the catalyst passing concurrently with the reactants through the reaction zone, generally at( a rate dierent than the rate of iiow of reactants. A third modiiication relates to catalytic materials which are non-miscible with reactants wherein the catalyst after being introduced at a plurality of points subsequently moves countercurrent to the reactants. In some cases there is a combination of the modifications, in which at least one reactant passes countercurrentlyto at least one other reactant, in which case the catalyst will move concurrently with one reactant and countercurrently to another reactant.

The choice of operating method, and the manner of applying that method, will of course be based on the type of catalyst, reaction and other factors. However, the choice of points for introduction of the catalyst and the rate at which catalyst is introduced at each point is correlated with change in temperature, change in concentration of reactants, etc., so as to compensate for such changes, as will now bemore fully described.

By the use of my invention I may so interrelate the various factors such as temperature; new rate of reactants, diluents, and catalyst; catalyst activity; time of contact between reactants and catalyst; etc.; as to provide a most complete and delicate control over the nature and extent of reaction at all points in the reaction zone.

As pointed out above, temperature control is possibly the maior problem in carrying out exothermic and endothermic reactions. .The present invention provides methods for maintaining proper reaction velocity in the face of increasing or decreasing temperatures, or of avoiding such increases or decreases in temperature.

In the case of endothermic reaction, the cata'- lyst may be introduced at a plurality of points spaced in the direction of now of reactants for concurrent ilow therewith. The amount of catalyst is smallest in the rst portion of the reaction zone, and largest in the last portion of the zone, due to the incremental additions of catalyst which occur along the pathL of now. The ternperatureA at the outlet of the reaction zone is considerably lower than at the inlet because the endotherrnal reaction takes up heat. The amount of catalyst added at each point is chosen so as Ato provide suiiicient additional catalytic activity to maintain the rate of reaction in spite of the lowered temperature existing at that point. Thus, even` though under ordinary conditions the rateoi reaction at a temperature, say 50 or 198 F., lower than the optimum reaction temperature would be several times less, resulting in much loweredconversion in thelatter portions or the reaction zone, the additional catalyst compensates at least partially for the lowered temperature and may maintain substantially constant conversion throughout the zone if added in sufcient quantity at each point. Another manner of utilizing this invention for endothermic reactions involves multipoint addition of catalyst with subsequent countercur'rent -flow relative to the reactants. This may be done I "especially :if lthe lsively adapted for use with "catalyst used undergoes very rapid deactivation at the ygiven reaction conditions. In this case, therate of introduction and Iiow of catalyst is regulated so that it is substantially spent, that is, deactivated for the reaction, by the time it exits from the reaction zone. The `point of exit of catalyst is at or near the point of entrance fof reactants. Accordingly, the reactants nrst Vcontact a relatively large mass of substantially deactivated catalyst containingr only a small proportion of 'active catalyst introduced at the later (earlier, with respect to reactants) points of the reaction zone. is quite limited, and smaller here than at subsequent points. As the 'reactants pass on through the zone, they contact smaller quantities ci total catalyst, but the catalyst contacted has greater activity. The deactivated catalyst also has a diluent effect, and a unit volumey of reactants passes through the rst portions of the reaction zone more rapidly than it does through the last portions. Flow of reactants continues counter-current to the flow of catalyst until just before leaving the reaction zone they come in contact with a relatively small quantity of catalyst having very high activity. AThe increasing catalyst ac'- tivity thus encountered by the reactants as they flow enable the reaction rate to be maintained in spite of the decreasing temperature caused by the endothermic nature ofthe reaction. The increments or catalyst added at the points of lowest temperature may, if necessary, be larger than those added at the points of higher temperatures.

the quantity added, rate of addition and rate of flow through the reaction zone always being so chosen and related as to compensate at least in part for the variation of reaction rate with texnperature. Alternatively or additionally catalyst regenerated at a high temperature may be used in such quantities as to maintain reaction teniperature constant or to minimize the extent of `temperature drop.

An exothermic reaction may be handled in a somewhat diierent manner, but with the saine end in view, namely, the control of catalyst aotivity and contact time between catalyst and reactants so as to compensate; in part at least, for variation of rate of reaction with temperature. Generally, the most satisfactory control is obtained by use of countercurrent now or reactants and catalyst introduced multipoint. Reactants rst are contacted witha relatively large volume of catalyst, the ratio of `catalyst activity' to volume of reactants being greatest at this point and progressively decreasing in the direction of reactant flow, While the temperature correspondingly increases. At the higher temperature levels, less catalyst activity is encountered, so that reaction velocity may be maintained as nearly constant desired. Near the exit from the reaction zone, the reactants are contacted with the smallest quantity of catalyst, this quantity, however, being suihcient to maintain the desired rate oi' reaction. The advantages of operating in this manner may readily be seen hycontrasting with prier methods wherein either the heat of reaction must be removed by difficult means heretofore discussed, er, if the temperature is allowed to increase, contact with equal increments-of catalyst combined with the higher temperatures causes greatly increased reaction rates. Another 'method of controlling exothe'rmic reactions which is particularly, although not'ex'ciucatalysts which te# come rapidly deactivated, is the concurrent flow of multipoint-introduced catalyst. In vsuchus:

The total activay age, a first-portion of catalyst is introduced either along with the reactant feed or separately into the reaction zone near the point of entrance of the reactants, and the next portion of catalyst, generally smaller, is added at a point at which the first portion is mostly deactivated; at any rate, the relationship of the amount of catalyst thus introduced to the extent of deactivation of previously introduced catalyst is such that the ratio of total catalyst activity to volume of re actants at that point is less than at the earlier point of catalyst introduction, the difference being generally inversely proportional to temperature. It would not be at all desirable to introduce catalyst increments of equal activity at equal points while the temperature is rising. As the temperature increases in the direction of flow of reactants, the catalyst activity decreases so as to avoid a constantly increasing conversion rate as would normally be encountered.

The alcove discussion is directed towards processes carried out under adiabatic, or at least partially adiabatic conditions in which the heat of reaction causes a temperature gradient to exist along the direction of ow of reactants. A combination of indirect or direct heat exchange to partially overcome heat of reaction, with the controlled introduction of catalyst as described above, may be used for exothermic or endothermic reactions.

1n case it is desired to maintain substantially isothermal conditions in endothermic or exothermic reactions by means of indirect heat exchange or other methods, this invention may be utilized to obtain a more satisfactory control of reaction and to simplify the temperature control. When reactants are passed through a stationary bed of catalyst, or contacted with a single portion of mobile catalyst, there is a tendency for the reacion to proceed too rapidly at first, with consequent overheating or cooling, as the case may be, at the rst point of contact between reactants and catalyst and too rapid catalyst deactivation at that point. However, by adding catalyst to the reaction zone in controlled increments in accordance with my invention, the extent oi reaction and temperature may be maintained under strict control since reactants are contacted with a limited portion of catalyst, and are not contacted with an additional portion until the temperature is brought back to the desired value. The catalyst is not added haphazardiy, but the addition is carefully correlated with the amount of heat produced or consumed by the reaction and with the amount removed or introduced, so as to avoid localized spots of overheating or excessive cooling.

Catalysts and reactants may now countercurrently or concurrently, depending upon the type of reaction, catalyst, etc., the proper modications being readily chosen in view of the detailed disclosures offered herein.

Other operating problems frequently encountered in catalytic reactions involve catalyst deactivation and means for avoiding same or for reactivating catalyst, the activity of which has dropped to an uneconomic level. Mobile catalysts are generally subjected to reactivation treatment either after each passage through a reaction zone, or a portion only may be treated each time to keep the overall activity at .the desired level. 'One of the advantages of mobile catalysts over stationary catalysts is that control of regeneration is thus obtained in a fairly simple manner. However. only the overall activity is thus affected,

l,theactualactivity at any particular point in the reaction zone being 'dependent upon conditions therein which are not readily changed with respect to deactivation of catalyst which is occurring. For example, many catalysts will be subjected to a rather extensive deactivation in a relatively small first portion of the reaction zone, due to temperature conditions, poisons, etc., with deactivation in subsequent portions of the reaction zone continuing at a much slower rate. In such a case, it will be seen that while the aver age or overall activity may be regulated, the uneven loss in activity causes an ineicient operation.

My invention provides a means for controlling the activity of mobile catalysts at any point in a reaction Zone. This may readily be accomplished by controlling the quantity and/or activity of catalyst introduced at the different points. Thus in certain cases, partially or completely deactivated catalyst may be admixed in varying proportions with fresh or reactivated catalyst to give the desired activity for introduction at any particular point. In fact, in some cases more than one different type of catalyst may be used for introduction at different points into a single reaction Zone to given controlled activity, which may be either maintained constant or varied from point to point to meet the needs of the particular reaction being catalyzed. Examples given herein will serve to point out more clearly a few of the many ways in which controlled variation or constant activity of catalyst is obtained and correlated with other reaction conditions through use of this invention.

Another method by which my invention makes possible a more effective use of catalyst is by controlling the quantity and/or activity of mobile catalyst in a reaction zone in relation to the concentration of reactants existing at various points in the zone. The change in concentration of reactants in a reaction zone depends upon the extent of conversion occurring. If, as in many cases, a substantially complete conversion of reactants to products is desired by the time the reaction mixture leaves the reaction zone, it will be seen that the concentration of at least one reactant must approach zero at the reaction zone exit. In many other reactions, however, an equilibrium may exist which prevents, or eco,- nomic considerations may make undesirable, a complete conversion. The extent of conversion may vary greatly with the type of reaction being catalyzed, one process involving say a one per cent conversion per pass while another may accomplish forty, sixty, or more per cent conversion in one pass. Ordinarily in case the percentage conversion is low, the loss in concentration of reactants as the reaction proceeds does not greatly affect the reaction rate. However, in the case of higher conversions ranging on up to per cent, the lowered concentrations of reactants existing in the latter parts of the reaction zone may greatly decrease the reaction rate, even though expedients such as using a large excess of one reactant or the like are resorted to. By controlling the multipoint introduction of catalyst in accordance with the decrease in reactant concentration, I may partially or completely compensate therefor, and avoid t0n great 0r any decrease in reaction rate by providing more catalyst activity at the points of lower concentration. The dilution eect of the catalyst is also to be considered. Again th Catalyst may pass either conc e urrently or counter- 'escasas catalyst activity,` reactant concentration, etc.,

may be used either alone or in various combinations, one with the other, as will be well understood by one skilled in the art in View of the full and complete disclosure given herein. Obviously the choice of one or 'a combination of methods of operating will have to be made with due'con` sideratioib for the reactions 'being catalyzed, the type Vof catalyst most suitable, .the extent of reaction,the thermal changes involved, the necessities and possibilities o f applying reactivation processes to the catalyst, etc. Various modifications such as -introducingdiluents refrigerants, heat carriers, reactants, and the like, multipoint along with or separately from the multipoint-injected catalyst, may be used as found advantageous for any particular process.

-A numerical treatment may be used at this point in order to bring out more clearly the herein'before discussed principles upon which the invention is based. A number of assumptions will be made to eliminate variables and simplify the presentation. A simple Aexample would be van endothermic conversion involving heterogenous catalysis, for example the conversion of an organic fluid using .a solid `contact catalyst in finely divided form. lThe data below will show how the invention `is utilized to `maintain a constant reaction rate by overcoming the effect of decreasing temperature, decreasing concentration of reactants, and any deactivation of the catalyst, which would, if the invention were not used but thefsame total conversion were obtained, cause the reaction rate to drop to a value in the last part of the reactionzone equal to only one-sixth that at the rst part of the reaction zone. Assume no change in volume of reactants upon reaction,` and assume that doubling the number of particles of catalyst willcausetwice as much reaction to occur in a given time due to the doubled area of catalytic contact surface offered the reactants.v Let a cylindrical reaction zone through which reactants and catalyst flow concurrently at thesame rate be considered as divided into six cylindrical increments of equal volume referred to hereinafter as unit volumes. Let 0.5 unit volume of reactants enter one end of the reaction zone per minute, and a total of 0.5 unit volume of catalyst enter the zone per minute in equal increments'of `0.083 volume at each of six equally spaced points; that is, 0.083 volume of catalyst is introduced into each of the six aforementioned incremental unit volumes of the catalyst zone. In the rst unit volume of the reaction zone, the ratio of volume of catalyst to Volume of reactants is ma me 140.083-'0917 in the sixth and last unit volume of the reaction zone. the ratio is Thus the ratio ofV catalyst to reactants vat the outletis f ...(og'fll times thatl at the inletfand accordingly, the. en. feet on the reaction rate would be to increasey the rate 11 times. Considering now the contact time, it will be seen on following 0.5 volume of reactants through the catalyst zone that it requires h 0.5 minutes to traverse the first unit volume of the zone and 0.5 minute to traverse the last unit volume of the zone. Thus it is seen that the contact time of reactants with the particular amount of catalyst present in the various zones is less in the later increments' of thereaction zone than in thev These iigures indicate quantitatively the tendency` toward increased reaction rate caused by the multipoint introduction of catalyst in the exact manner just described, which tendency may be used to maintain a substantially constant overall reaction vrate by-eounteracting the effects of such changes in reaction conditions as drop in temperature due to the endothermal nature of the reaction and/or decrease in concentration of ref actants, etc., to the extent that any of such changes in conditions, or the effect of all combined, tend to cause a six-fold decrease in reaction rate. Insimilar cases in which. the depressing influences `on the reaction rate are greater or less than six fold, the rate would be held constant by a ,corresponding increased or decreased overall ratio of catalyst to reactants, or by a controlled change in the activity of catalyst introduced at succeeding points, etc, the exact conditions being calculated in a manner similar to that shown above.' Application of this type of procedure toa specific endothermal reaction will be described in more detail hereinbelow `with reference to Figure l. In order to explain the invention more fully, the following examples andappended drawings are provided to illustrate speciiic embodiments of the process, but no limitations -are thereby implied, inasmuch as the in,- vention may be utilized in numerous other` manners by following the teachings of this disclosure.

Figure 1 shows ,in diagrammatic form an are rangement of equipment for carrying out the catalytic cracking of petroleum oils, an endo-l thermic reaction, using a finely divided solid cartalyst suspended in vaporous reactants andl thus flowing concurrently therewith, commonly termed lluid catalyst process.

Figure 2 shows diagrammatically apparatus for polymerizing butenes, an exothermic reaction, in which a gaseous catalyst immiscible with the liquid reaction mixture is pased countercurrently to the reactants.

`.F.islirc ,3 isa diagrammatic, drawing Qf. vappart-9 with economy of equipment.

i1 tus used for the vapor phase reduction of nitrobenzene with gaseous hydrogen, an exothermic reaction, wherein a metal catalyst supported on a solid granular carrier material is passed concurrently with, but at a different rate than, the reactants. Y

Figure 4 shows diagrammatically an apparatus and flow of materials therethrough wherein a mixturev of carbon monoxide and hydrogen is converted into hydrocarbons and/or oxygenated organic compounds using `a powdered catalyst in a plurality of beds of varying intensity, the catalyst also being reactivated to varying extents in a plurality of beds.

Figure 5 shows diagrammatically one form of apparatus and flow of the materials therethrough for converting olens plus carbon monoxide and hydrogen into alcohols by the so-called Oxo process.

It will be understood, of course, that numerous items of auxiliary equipment, such as pumps, valves, heat exchangers, controllers, and the like, are not shown in the drawings for the sake of simplicity, and these items will be readily supplied by one skilledin the art in view of the present disclosure.

In Figure l, the reactant, for example gas-oil derived by straight-run distillation of crude pctroleum, passes from line I into blower II, and thence through line I2 into heater I3 wherein it is raised to a suitable temperature such as 900 F. for the initiation of the reaction upon contact with the catalyst. From heater I3 the heated reactants are sent through line I4 into the reaction chamber I5. This reaction chamber may take the form of an elongated tube, as shown diagrammatically in Figure 1. Various types of reaction chambers suitable for use with powdered catalysts are known in the art. A very nely divided solid catalyst is iniected into reaction chamber I5 at spaced points along the path of flow of reactants through lines I6, I1, I8, and I9. Obviously, although only four lines are shown, the-number of such lines may be varied at will to obtain suitable operating conditions compatible The catalyst may be of the natural clay type such as fullers earth, bentonite, etc., preferably activated in known manner, or of the synthetic type such as silicaalumina, or other effective catalysts, for example bauxite, known to the art. The method of introducing the nely divided catalyst into the reaction zone may include such operations as suspension in liquid or gaseous reactants or diluents.

The catalyst may enter lines I6, E'I, I8, and

I9 from two sources. The first source is conduit 20 which carries recycled catalyst which has been partially deactivated by previous use in the process. The second source is conduit 2| which carries regenerated catalyst from catalyst regeneration zone 22. Carbonaceous deposits are removed from the catalyst in Zone 22 by burning in an oxygen-containing gas. The quantity of catalyst from each source injected at each point is regulated 'by suitable means so that all of the catalyst entering through line I6 is the partly deactivated catalyst from conduit 20; most of that entering through line I1 is of the same type, but has admixed with it by means of line 23 a small portion of freshly regenerated catalyst from conduit 2I. that entering through line I8 has a larger porportion of reactivated catalyst, which reaches line I8 through line 24; and that entering at the last point through line I9 is comin the increments introduced along posed entirely ofregenerated catalyst from conduit 2 I.

The mixture of products, excess reactants if any, and catalyst passes from reaction zone I5 through conduit 25 into ,a catalyst separation zone 25, which may be a cyclone separator, electricalprecipitator, or any other suitable means for accomplishing the separation of finely divided catalyst from the hot vapors. Catalyst passes from Zone 2E into conduit 21 and a portion is taken from conduit 2-1 through conduit 28 to the catalyst regeneration Zone 22. Vapors leave the catalyst separating zone 2B through line 29, and may be condensed and fractionated to separate out the desired cracked gasoline product, with unreacted gas-oil being recycled to the reaction chamber. If desired, various other modifications of such a cracking process which are known to the art, for example recycle of very small amounts of hydrogen, use of steam diluent, etc., may be used.

The cracking of petroleum oils is an endothermic process, and, as heretofore explc ined, under ordinary methods of operation a substantial temperature drop occurs which causes a decrease in reaction rate as the reactants proceed through the cracking zone. However, by controlling the relative volumes of partially de,r ctivated and of activated catalyst and also the total volumes of the catalyst introduced into the reaction zone as just described, in conformity with the principles heretofore discussedin detail, the total catalytic activity at e.r ch succeeding point in the cracking Zone in the direction of flow of reactants is greater than the activity at the preceding points, the increase in activity being such that the normal decrease in reaction rate accompanying dropping temperatures and catflyst deactivation is partially or completely obviated. This increase in total catalyst activity is obtained by the increasing volume of catalyst due to its multipoint introduction, and the increasing activity of the catalyst introduced, due to the use of relatively gre: ter proportions of freshly reactivated catalyst the path of flow of reactants. Of course, the actual quantities of catalyst introduced at the various points will depend upon thecatalyst being used, its rate of deactivation under the given reaction conditions, rate of flow of reactants :nd catalyst, extent of reactivation effected in the catalyst regeneration zone, the characteristics of the gas-oil being cracked, temperature and pressure conditions in the cracking zone, extent of indirect heat exchange occurring between the cracking furnace and :ny outside sources of heat or cooler surroundings, etc. However, the general principles set out in this disclosure will readily enable one skilled in the art to correlate these various factors for any particular application to obtain the advantages of the invention. Although in the drawing the rstpoint of catalyst introduction into the rei` ction zone is shown past the reactant inlet, this first point may also be positioned at or just before the inlet so that the first increment of catalyst enters along with the reactants.

It will be noted that in the cracking process as shown in Figure 1, several of the aspects of my invention which were described before in some detail may be involved. For example, the endothermic nature of the reaction will, unless sufficient neat exchfnge is provided, cause the temperature to drop. The multipoint introduction of catalyst is so controlled as to counter-balance this eiect in order to maintain desired reaction velocquantities as to compensate for the deactivation in concentrr tion of reactants which occurs as the reaction proceeds. Since in a gas-oil cracking process of the type described, only partial conversion, s ay from 15 to 40 per cent, is permitted to the case of reactions giving complete conversion in a single pass. However, any eiiect of this kind. is readily overcomev by the controlled sddition of catalyst at the different points along the cracking zone.

Thus it is seen that in a typical process, gasoil cracking, control of catalyst addition maybe related to several variables. On the other hand, weil known expedients might in some cases be utilized to control certain of these variables. For exemple. sufficient heat may be introduced into the cracking .acne by various means as to maintain a substantially constant temperature, al though this is diiiicult to accomplish in actual practice, at least by direct means. In such a cr se, catalyst addition at points would be controlled to make up for the combined effects of loss in catalyst activity and change in reactant concentra,-V tion. On the other hand, reaction conditions mcy be maintained which are so mild that the amount of catalyst deactivation occurring in a single passv will be very slight, so that the principal purpose of introducing the catalyst at points will be to compensate for decreasing temperrtures and/or concentration of reactants in orderto maintain a substantially constant reaction rate. v,

In Figure an elongated reactionchamber d is provided, the interior of which mayibe filled` with packing materiel for promoting intimate contact between gases and liquids. Fed to the system through line el is a gaseous hydrocarbon mixture containing a substantial proportion of butenes. preferably isobutvlene although normall butenes may also be present. This gas` is compressed in compressor d2 and then passes vial line.` @3, to heat exchanger lili where it is cooled by indirect exchange with effluents from the reaction chamber. From the heat exchanger the cooled hydrocarbons pass via line d5 into the top of reaction chamber iii, wherein they are subjected to the polymerizing action of boron trifiuoride' (BFS) as hereinafter described. Refrigeration means is is interposed in line 45, end serves to cool the reactant feed to the desired reaction temperature, in this case 30 vC. The hydrocarbons making up the feed are in liquid phase at this' temperature, and the reaction chamber is operated at substantially atmospheric pressure.`

Ordin: rily a C4 fraction is used which contains substantial amounts of butanes, which serve as a diluent andas a solvent for the high molecularv weight polymers formed in the reaction. If such butanes are not available admixed with vthe butenes, they may be supplied, or pentane or other suitable srturated hydrocarbon` solvent Amay be, used. The liquid butenes and accompanyinghy-l drocarbons ow downwardly in chamber 40 coun--Y tercurrent` to gaseous BFS and gaseousl propane, and substantially complete polvmerlzatlon 0f` thef bufen'es oscurato form polymers, of: a,.mo1ecular.;

continuously contacts upwardly `in catalyst. In order lwhich each increment added tothe weight suitable for usef'aslubricating oils. addi-e tives to oils,` etc.

The boron fluoride catalyst passes from con-v duit 41 into reaction. chamber 4i) at a plurality of points by meansvof valved elusive. Also introduced into chamber :lil at the vsame points is liqueed propane from conduit 139 via valved lines 5A-56G inclusive. This liquid propane :cts as a coolant, diluent, and disperant for the BFS, as will be'explained in more detail below. Ordinarily a catalyst activator such as hydrogen uoride, or other materials which will cause the production of hydrogen. halides in the reaction zone, is introduced in small amount along with the boron fluoride` or otherwise. Fur thermore, metallic nickel or other metals are occasionally used in the reaction zone to help catalyze or promote the reaction.

' The butenes upon first entering chamber 40 and beginning their downward ow therethrough come into contact with a gas phase which comprises propane and BFa. The volume of the gas phase is greater at this point then at any other i point in thechamber. Polymerization is initiated by-'the catalytic action of the boron fluoride. ,This polymerization reaction is highly exthermic, and the temperature must beheld under very careful control, particularly since the type of productl obtained may change greatly with a relatively small change in temperature; that is, the-product formed :at-*30 C. may have an average molecular weight several times that of the product formed at 0 C. For this reason, itv is preferredy to carry out the reaction asnearlyisothermally as possible..

The amount of boron Afluoride introducedwill ordinarily vary from point to point, beingv smallest at the top point (conduit 48A) and greatest atv the 'bottom ,point` (conduit 481Go. `By this multipoint addition of the catalyst, a muchmore eicient reaction control is realized, since' the reactants do not contact. theV total' amount of catalyst at` once. The catalyst contacted at theiirst point comprises. notv only, thatintroduced. through conduit 48A, but also any bubbling up from the lower part of the reaction chamber.' Just enough is introduced` through 1ine. 48A to furnish suicient fresh catalyst to initiate' the reaction to the desired extent. It will be seen that the downward-owing reaction mixture. flowingv catalyst. Due'to the formation ofcomplexes between boronV fluoride and oleiins, a. substantial part of the catalyst combineswith reactants and is carried down as complex. Such complexes have only a limited amount of catalytic activity, ifat all.

Thus, if all the catalyst, were introduced at the bottom, it would be continuously` reactimgwithv oleiins as it rose through thel chamber, and the upper part of thechamber would be deiicient.r

to ensure that some catalyst reaches the'tcpy ofthe chamber, an otherwiseunnecessary excess would have` to beim troduced at they bottom. Much` betterv results areobtained by the multipoint addition, by gas phase owing upward through the reaction chamber` can be controlled inv amount to give-just the desired concentration of catalyst at theV givenpoint.- It is preferable that the amount of catalystV be relatively small at the top of thechamber where the reaction starts, since the major4 part ofthe reaction; andl thus heat evolution generally oc' curs, in` the, upper half of the chamber where the vgreatest yconcentration of monomerslisifound;

Thesintroductonsofxcontrolledzamountsiofxcoldi at points along with the catalyst gives effective control of temperature throughout chamber` t0. rlhe propane vaporizes immediately upon entering the chamber, and in so doing absorbs the heat of reaction. Of course, additional indirect heat exchange may be provided for chamber iii to assist in removing the heat of reaction if desired, particularly in order to avoid having too large an amount of gaseous propane passing through the reactor. A convenient way to do this is to pass chilled liquid propane through coils in chamber d in indirect heat exchange with the reactants, and then to pass the desired amount of the propane into conduit i9 for direct introduction through conduits 50A, 5GB. etc.

Since the amount liquid propane of BFS used is only a small percentage or" the hydrocarbons charged, say from 0.5 to 5.0 mol per cent, the propane gas 1s very eiective in promoting a more thorough dispersal of the catalyst throughout the reaction zone. 1t also serves as a diluent both for the liquid reactants and for the gaseous BFa. For this reason, larger amounts o BFS may be passed through reaction chamber it thus admixed with propane than would be suitable in the absence oi the added gas. This excess BFs is recovered and recycled. The amount of liquid propane added through the lower conduits, for example, EG to '50?, is less than that added through the upper conduits such as SBA and 50B. This is because more heat of reaction is developed at me top of chamber to than at the bottom, and more evaporation of propane is needed at the top to maintain the desired low temperature.

Flow rate of reactants through chamber de is preferably such that substantially no unpolymerized butenes are present in the eiiiuents and the polymers in the eiiuents are predominately of high molecular weight, 'for example over 2000. The character of the polymers can be controlled to a certain extent by controlling the reaction time and thus the extent of conversion, although a change in operating temperature will generally have more influence on the final product. n A short conversion time will ordinarily produce some of the high molecular weight polymers, with a larger percentage of intermediate polymers which may be used for diierent purposes or which may be recycled to reaction chamber d0. The volume of propane gas passed through reaction chamber lil will generally be several times the volume of liquid reactants and solvent passed through the chamber in a given time.

Propane gas and boron fluoride gas leaving the top of chamber i0 via line 5| are compressed in compressor 52, chilled, by partial evaporation in known manner, if desired, in refrigeration means 53 to condense liquid propane, and then passed to accumulator 54. Cold gaseous boron fluoride leaves the top of accumulator 54 through line t1 for re-use in the process, While cold liquid propane leaves the bottom of accumulator 54 by line GS to be introduced into chamber 40 as described above. Of course, the gas phase from accumulator 5d contains some propane, and the liquid phase contains some boron iluoride in solution.

Since butenes are appreciably volatile at the temperature of operation of chamber 40, the gas leaving that chamber via line 5l has some butenes in it, and these butenes tend to undergo some polymerization in line 5| and compressor 52. For this reason, it isdesrable .that the length of line 5l between chamber Sil and compressor 52 be short, and that the line 5| and compressor be ushed periodically with a solvent for the polymers such as liquid butane. Not much trouble is experienced from compressor 52 on, since liquid propane is present which acts as solvent. The amount of polymer formed is small compared to the amount of butenes passing through this part of the system, most of the butenes returning unchanged into reaction chamber fr0 along with the propane. A very satisfactory way to obviate any diiiculty in this regard is to wash the gas in line 5l with suicient liquid butane or pentane to remove practcally all of the butene. The liquid may then flow directly into chamber ci. rlhis modification is not shown in the drawing for the sake of simplicity.

Liquid products leave the bottom of reaction chamber t0 through line 55 and pass through heat exchanger ai to be warmed to a higher temperature and to cool the incoming butenes. From exchanger di the products pass via line 5S to separator 5l wherein dissolved and/or entrained boron iiuoride and propane gas are evolved, which pass via line 5S to line 5l for recovery and re-use. Liquid products pass from separator 5'! via line 5e to boron fluoride and solvent recovery means which are indicated diagrammatically at 0U. lThe solvent, which ordinarily is butane, is recovered by evaporation and leaves the system thro-gh line el. Part or all of the solvent may of course be recycled to line il or elsewhere if desired. Boron fluoride is recovered from its complexes by heating or other means, and is returned to the system by lines 62, 53, and 5i. Grdinarily heating the product to C. or higher will serve to release at least part of the boron :Fluoride from the hydrocarbons. Polymer is removed from the system at 63. Any make-up BFS and/or propane required may be supplied through line i.

`The above-described process exemplifies an adaptation of my invention to a highly exothermic reaction wherein the temperature is maintained constant. The multipoint addition of catalyst is controlled with respect to two principal variables. One is the loss of catalyst by complex formation. Catalyst is added at points to maintain the desired amount of active catalyst. The other is change in concentration of reactants. The smallest concentration of catalyst is maintained at the point of greatest concentration of butenes, while the greatest concentration of catalyst is at the outlet where reaction is being completed with practically no butenes remaining. It is to be noted that due to the diluent effect of the gaseous propane, the actual quantity oi` catalyst may under certain conditions be greater at the top point than at the bottom point, but the ratio of catalyst activity to reactants decreases from bottom to top, the diluted catalyst having less eiect than the undiluted catalyst. The catalyst activity thus changes in relation to the extent of reaction, to compensate at least in part for the tendency toward decreased reaction rate.

An important aspect of the polymerization process as described is the fact that, while actual cooling is accomplished by the propane, temperature control is effected to a large extent by the multipoint addition of the catalyst. This is because the rate of addition of catalyst at each point is so controlled and correlated with the other factors that catalyst activity at the point of greatest tendency toward heat evolution, that is -the butene inlet, is smaller than at any other rtion of catalyst and/or reactants is resorted to,

and the reaction time is unduly'extended because of the inherent limitations of that method of operating.

In Figure 3, the reaction chamber 'I0 is preferably provided with means (not shown) for removing at least most of the heat of reaction by indirect heat exchange. A certain amount of heat is also lost to the atmosphere, but in order to avoid uneven cooling the entire chamber is ordinarily provided with some insulation. Heated vaporized nitrobenzene from line 1| and hydrogen from line 'i2 join in line 13, and flow into reaction chamber il for downward flow therethrough. The hydrogen may be admixed with k,

substantial amounts of carbon monoxide, or with inert gases such as methane or nitrogen. In fact, in carrying out the reduction of nitrobenzene in accordance with the present invention, I prefer to have some inert gas with the hydrogen. The ratio of hydrogen to nitrobenzene must be held `within relatively narrow limits to obtain the highest yield of aniline, since a ratio considerably higher or lower than the stoichiometrical amount gives rise to reduction products other than aniline. It is best to have somewhat more than the theoretical ratio of hydrogen to nitrobenzene, but not too much more, in order to ensure completion of the reaction, and some inert-gas is preferably used in admiXture with the hydrogen.

A suitable supported hydrogenation catalyst in granular form is caused to pass through conduit 14 into manifold l5. Branching o from manifold I are branches 16A-'EBF inclusive through `which the catalyst is introduced into the reaction chamber it at spaced points along the path of flow of reactants. The quantity of catalyst introduced through each branch 'i6A, etc., may be controlled by any suitable means. It will be appreciated that due consideration must be given to the fact that chamber l0 is operated under pressure. The lines, '15A to FGF inclusive, are

, shown equally spaced; however, the lines may be more or less in number, and evenly or unevenly spaced, in accordance with the capacity of the system, convenience of fabrication, operating conditions, rate of catalyst introduction at the various points, and economy of equipment. A series of baliies il is provided in chamber 'l0 to keep the catalyst particles dispersed and in good contact with reactants as the catalyst falls to the bottom of chamber l0, These baiiies preferably have only a slight inclination from the horizontal so that catalyst is more or less pushed off of one baiile to the next by incoming catalyst.

In the hydrogenation of nitrobenzene by prior methods, the reaction mixture is passed through a stationary bed of catalyst. Since the concentration of reactants is greatest in the rst portions of the catalyst bed, the major part of the reaction occurs before the bed is halfway traversed. This means that the amount of heat liberated in the proper parts of the catalyst chamber is greater than in the lower parts, and thus the load on heat exchange coils or the like with in the nitrobenzene and hydrogen gas is which the chamber may be provided is greatest at the top and least at the bottom. Thus the heat exchange means must either be oversized at points or is overloaded. In practical operation, the heat of reaction cannot be satisfactorily removed, and a serious temperature rise occurs. This is very undesirable, since the optimum yield of aniline, when using any given catalyst, is obtained only in a relatively narrow temperature range. Sintering of catalyst is also likely to occur on the most active catalytic points where the actual temperature may be from 25 or 50 to a. hundred or so degrees centigrade higher than the mean temperature or the reactants and catalyst near those points. A further disadvantage lies in the iact that the temperature rise serves to increase the already excessive reaction rate still more.

By means of my invention the catalyst addition is controlled in accordance with the rate of reaction or rate of evolution or' heat, so that substantially equal, or at least regularly varying quantities oi' neat are evolved and removed along equal increments or' the length 0i' reaction chamber i. '.l'hus, in the nrst pai't or reaction chamber ttl, a relatively small amount of catalyst is introduced through branch itA. Since the highest concentrations or' nitrobenzene and of hydrogen are found in this portion or the reaction zone a small amount of catalyst is suicient to promote considerable reaction. As the reaction rate tends to lessen due to the diiuent eii'ects of the aniiine formed, or stated another Way, due to the lowered concentrations or nitrobenzene and hydrogen, additional catalyst enters the reaction Zone through NB, and the reaction rate tends to increase again. Thus, the quantity of active catalyst surlace present at various points in reaction chamber le is maintained sufhciently, as the reactants ilow therethrough, so as to give a completely reduced product in the efiuents. The amount of catalyst in the parts of chamber 'it is small at the inlet thereof, and increases gradually toward the outlet, where it reaches a maximum. The reaction rate is maintained more or less constant throughout the reaction zone, in contrast to other methods wherein the last half of the catalyst chamber may be used for effecting only five or ten per cent of the total conversion. The temperature may be maintained substantially constant due to the fact that the amount of heat liberated is not excessive at any point, or a gradual temperature gradient may be allowed to exist, an increase of say 50 C. from the inlet to the outlet being permissible without undesirable effects. It is to be noted however, that in using my invention, such a temperature gradient is regular, and is obtained gradually as the reactants flow through the apparatus, rather than being obtained all at once as by other methods. in which case a peak temperature may even occur. with a subsequent falling oli in the latter stages where very little reaction is occurring.

A certain amount of catalyst deactivation will occur which tends to lessen the reaction rate, and this is also compensated for by the fresh catalyst added. The rate of catalyst deactivation will of course depend upon the catalyst used, the severity of reaction conditions, and particularly upon the purity of the reactants. Generally, the amount of catalyst poisons present small,

. and catalyst deactivation is not of great consequence in lessening the reaction rate in the passage of catalyst from one catalyst. of catalyst is maintained through chamber l so thereof is usually still fa'rly active.

chamber '16 will be many Avolume basis, than the rate of therethrough.

able conveying duit i4 for re-use in the process.

` vpassed through a 'Y tially its original conditions.

of catalyst, rather than a portion, may be passed through regeneration zone 83 passed to point to the next in reaction chamber 10. The relative rates at which catalyst is introduced at the various points will be determined as described above with reference to control of rate of reaction, while the total rate of catalyst flow into and thence out of chamber 1E) will generally be chosen with respect to the type of reactivation treatment to which the catalyst is subjected outside the chamber.

`It is usually preferable to reactivate the catalyst before it has lost too much of its activ'ty, since considerably higher temperatures frequently must be used in the reaction zone with a less active Thus it is seen that a continuous now that the catalyst as removed from the bottom The rate of flow of gaseous reactants through the catalyst times greater, on a ow of catalyst The total efluent from reaction chamber i0 passes out through conduit i8 and then to catalyst separator 19 where the catalyst separates from the gases by gravity. This catalyst is removed through conduit 83 containing suitmeans such as screw Sl. From 80 the catalyst passes through conduit 8'2 to con- A portion of the catalyst stream may be continuously byregeneration zone indicated diagrammatically at 83 to maintain the total catalyst stream at the desired activity. The regeneration in zone 83 comprises conventional chemical treatments to remove accumulated impurities and to restore the catalyst to substan- The entire stream if desired.

The gases in catalyst separator 'i9 comprise aniline produced in the process, any traces of unreduced nitrobenzene, steam formed as a byproduct, any excess hydrogen, and any inert gas Y' introduced along with the hydrogen. This gas phase is passed via line and into product separator 86, wherein a liquid water-rich phase, a liquid aniline-rLch phase, and a gaseous phase separate out. The gas is re- 84 through cooler S5 cycled via line 8l to line 12 for re-use of the hydrogen in the process. In order to prevent inert gases from pyramiding in the system, a

' portion of the gas is allowed to leave line 8i through valved branch 88. The aniline is removed from separator 86 through line 89 and suitable apparatus for removing dissolved water and any other impurities. Water is removed from separator 86 through line 90, and passed to a system for recovering v aniline therefrom.

- accomplishing this is to extract the aniline from v the water with nitrobenzene, the extract then dissolved One very effective method of being led to the reaction zone for reduction of the nitrobenzene.

Suitable catalysts for the reduction of nitrobenzene according to the system just described may comprise metals such as gold, silver, nickel, copper, or t'n, either alone or in admixture, and preferably supported on granular carriers such Vas pumice, porcelain, alumina, etc.

It is necessary that the catalyst composition have sufficient the eiects precipitated hydroxide or carbonate. With such a catalyst, an operating temabout 275 C. to 375 C. is suitable.

The processes described above with reference to Figures 2 and 3 have illustrated two specific methods of eifecting exothermic reactions, viz., polymerzation and hydrogenation, respectively. It will be appreciated that some of the principles of the invention and procedures described herein will be applicable to exothermic reactions as a class, with suitable modifications being made in View of particular known characteristics of specinc reactions which may differ from one reaction to another. Thus, polymerization reactions broadly are comprehended within the scope of this disclosure. Polymerization may be broadly considered to be any chemical combination of two or more similar molecules to form a single molecule, the reaction usually involving primary valence forces. The combining molecules may be all of the same k'nd, or they may be of two and possibly more types. The most common and largest number of polymerization reactions involve organic molecules which contain an unsaturated carbon-to-carbon linkage, for example, a double bond. Polymerization in the presence of a gaseous, liquid, or solid catalyst may be carried out with the reactants in the vapor or liquid phase, at high or low temperatures and at high or low pressures. The operating conditions are known and will vary according to the reactants, the catalyst, and the type of products involved. Many types of polymerization are known, for example, the reactions involving vinyl compounds such as styrene and vinyl chloride, unsaturated acids, ketones, nitriles, and the like, olens, diolefins, acetylenes, and condensation reactions of aldehydes, urea plus formaldehyde, etc.

One preferred modification comprehends the polymerization of low-boiling olens at elevated temperatures to form liquid fuels. For example, a mixture of three and four carbon atom hydrocarbons containing propylene and one or more butenes, and preferably containing considerable quantities of isobutylene, is passed upwardly in the vapor phase, or in the l' quid phase, through an elongated reaction zone countercurrent to a downwardly flowing stream of granular synthetic silica-alumina type polymerization catalyst. Such catalysts are made from hydrous silica gels activated with minor amounts of alumina or zirconia or other metal oxides and are well known in the art; hence detailed discussion of their composition is not necessary at this point to a full understanding of the invention. This type of polymerization w;ll take place in the presence of an active catalyst at temperatures of about 250 F. However, the reaction is not particularly sensitive to temperature, and satisfactory products may be obtained at temperatures within the range of say 250 to 400 F. or even somewhat higher. The reaction is of course highly exothermic and due to the lack of sensitivity to temperature just mentioned the temperature may be allowed to rise substantially in the direction of ow of reactants through the reaction zone without adversely affecting the iinal products. While some heat exchange may be employed in order to minimize the temperature rise it is not necessary to remove all the heat of reaction when operating in accordance with the present procedure. This desirable result is obtained by introducing the granular catalyst into the reaction zone at a plurality of points along the length thereof, the quantity and activity being cont-.roued 21... in accordance with the principles hereinbefore outlined so that as the reaction mixture proceeds upwardly in the reaction zone the activity of catalyst encountered is substantially constantly decreasing; in this connection by activity I mean the total catalyst activity available, as aiected by quantity and/or activity of a given portion of catalyst.

The catalyst may be introduced by known means and allowed to move slowly down through the reactor, for example in a reactor constructed similar to that shown in Figure 3 which includes bailies for slowing the flow of catalyst. In this modification the reactor is not maintained full ,of catalyst but rather the catalyst is allowed to move slowly down from one baille to another. Thus, the reaction mixture when first introduced contacts a maximum of catalyst at a minimum inlet temperature. The inlet temperature is chosen with respect to the particular catalyst and reactants so that in the presence of the particular quantity of catalyst present in the lower part of the reaction zone the reaction will be initiated. As the reaction proceeds upwardly, the temperature tends to increase due to the exothermic nature of the reaction. This increase in temperature causes an increase in reaction rate which would soon cause the reaction tofrun away if the same amount of catalyst were being contacted. However, in the practice of this invention the amount of catalyst in the reaction zone constantly decreases in the direction of ow of reactants and this decrease in catalyst tends to oil-set the eiiect, on the reaction rate or extent of reaction, of the increasing temperature just mentioned. While the decrease in concentration of reactants in the direction of flow of reactants tends to cause a decrease in reaction rate, the heat liberated is suiicient that the Atemperature can be allowed to increase to such extent that the eiect of temperature on the reaction rate will more than overcome the eiect of decrease in concentration of reactants. By contacting less and less catalyst as the reaction mixture nears the top of the reactor the overbalancing effect of temperature is compensated for. As an example, the inlet temperature may be 250 F; and the outlet temperature at the top may range from 350 to 400 F. with catalyst of the usual activity.

If the reactor is maintained substantially full of catalyst so that it moves downwardly therethrough as a moving bed thus dispensing with the use of baiiles, the activity of catalyst introduced at the various points must be controlled so that the activity in the upper portions of the moving catalyst bed is less than the activity in the lower portions. This can be done by partial regeneration of the catalyst and blending of reactivated and unreactivated catalyst in varying portions as described hereinbefore. In any manner of operating, part or all of the unreactivated or reactivated catalyst may be introduced into the reaction zone at a temperature considerably lower than the reaction temperature in order to take up at least a part of the heat of reaction, or this may be supplemented by or replaced by indirect heat exchange means.

Another method of polymerizing oleiins or other unsaturated organic compounds is to operate as described above with reference to Figure 3, the temperature being maintained constant or at least the temperature rise being greatly limited by use of indirect heat exchange or otherwise, ybut the heat exchange requirements 22" in the various sections of the reaction zone being equalized by virtue of the controlled introduction of catalyst as described.

Another conversion process in which the principles of the invention are applicable is that commonly known as the Fischer-Tropsch synthesis, in which hydrogen and carbon monoxide are reacted to form hydrocarbons suitable for use as fuels. By control of ratios of reactants, temperatures, contact times, and catalysts, the products may range from gases to solid waxes, and from essentially hydrocarbons to essentially oxygenated hydrocarbon derivatives. The particular process of this type of commercial interest at the present time involves the reaction of a synthesis gas containing about two mols of H2 to one mol of CO, in the presence of a cobalt or iron catalyst, to form gasoline-boiling-range hydrocarbons, along with substantial amounts o1 oxygen-containing aliphatic compounds including alcohols, aldehydes, ketones, acids, and esters. The reaction is believed to involve a preliminary formation of methylene, i. e., -CH2-, groups, several of which unite or polymerize to form at least some of the reaction products, and hence may be broadly thought of as involving polymerization as well as other reactions. However, the over-all conversion has characteristics distinguishing it from other conversions. Ordinarily the temperature must be controlled Within very narrow limits to produce a given product, and since the reaction is highly exothermic this involves the removal of large quantities of heat from the reaction zone. In some instances, however, a limited temperature rise may be permitted. Application of various principles of the present invention as set forth hereinabove will be apparent on consideration of the specic attribues and requirements of the Fischer-Tropsch type synthesis.

For example, the procedure just described in which oleiins are polymerized in the vapor phase in the presence of a granular catalyst moving countercurrently to the reactants, the temperature being allowed to rise appreciably in the direction of ilow of reactants, may be used for the synthesis reaction provided the temperature rise is limited, by removal or absorption of some heat of reaction, to a smaller figure than that allowable in the polymerization of oleiins. Thus, with a reduced iron oxide catalyst, a H2:CO ratio of 2:1, and a reaction temperature in the neighborhood of 600 F., the inlet temperature may be 575 F. and the outlet temperature 630 F., only suilicient heat being removed by heat exchange coils or tubes in or around the reactor or by other known methods to establish a regular and deliberate temperature rise; the catalyst in pellet or even powdered form is passed into the vertical reactor at a plurality of points and passed downwardly through the reactor, removed from the bottom, and returned, with or without reactivation, to the inlet points again. The higher the temperature the less catalyst contacted by reactants, with consequent advantages and results as described hereinabove.

If desired, the procedure of Figure 3 may be used for carrying out the Fischer-Tropsch synthesis, whereby temperature is held constant by removal of heat, catalyst and reactants ow concurrently, and the increasing amounts of catalyst encountered along the line of ilcw overcome the effect of the decreasing concentration of reactants. Likewise, heat removal and temperature control are made easier as described by 23 providing a more nearly equal extent of reaction throughout the various sections of the reactor.

The use of powdered reduced iron oxide catalyst has proved to be of great advantage in this reaction, and this catalyst may be suspended in an upflowing gaseous reaction mixture, the suspension being passed through vertical heat exchange tubes or contacted with other heat exchange means for removal of the heat of the Fischer-Tropsch reaction. Additional catalyst is introduced at a plurality of points along the length of the reactor, and an advantageous method of constructing the ractor is to superimpose a series of vertical tube bundles, a space being provided between each two bundles by means of horizontal tube sheets into which space catalyst is injected; the space also serves to ensure re-mixing of reaction mixture and catalyst at several points along the line of flow. With or without the use of such heat exchange tubes, the velocity of gas flow may be sufficiently low to provide a so-called hindered settling of catalyst, by which all catalyst is eventually carried upward and out, but the average rate of flow of catalyst is less than the rate of ow of gases, thus increasing the density of the catalyst suspension. This is particularly desirable when the catalyst, as in this case, is only slowly deactivated.

In any of the foregoing methods of carrying out the synthesis of organic compounds from hydrogen and carbon oxides, the activity of catalyst introduced at each point may be separately controlled by any suitable means, includ ing the proportioning of unreactivated and reactivated catalyst. Speciiically, the procedure of Figure 1 above may be utilized in any of the concurrent flow methods in order to provide increasing activity in the direction of flow to minimize the decreasing extent of reaction which would otherwise occur because of the decrease in concentration of reactants. This is particularly desirable when per-pass conversions of 80 to 90 per cent or more are obtained, which is not unusual for this reaction.

Another method of eifecting a Fischer-Tropsch synthesis reaction embodying certain principles of my invention is illustrated in Figure 4. In that figure, reaction chamber and reactivation chamber lil are provided. Each contains a plurality of horizontally disposed perforated plates iii. Above each plate there is maintained a fluidized bed |03 of powdered solid catalyst, preferably reduced iron oxide promoted with alumina, potassia, and calcium oxide. Within the reactor |80 i'ive such beds are shown, plus a bed in the bottom of the reactor which acts the same way, but more or fewer may be used. The IIs- CO synthesis gas, including recycled tail gas, is introduced at the bottom of reactor |00 through inlet conduit |04 and passes upwardly through a mass of powdered catalyst maintained in fiuidized condition in the conical bottom of reactor |00 and thence upwardly through each of the perforated plates |02 and fluidized beds of catalyst |03 to the top of the reactor. The carbon monoxide and hydrogen reacts in the presence of the iron catalyst to form hydrocarbons and oxygenated chemicals. A gas comprising these products, any unreacted hydrogen and CO, and any diluent gas, passes through one or more cyclone separators |05 and thence through line |96 to conventional fractionation and related equipment for recovery of products and recycle Ordinarily a high recycle ratio of tail gas, which is rich in hydrogen', to fresh feed gas is used, for example a 4:1 recycle ratio. This aids fluidization of the catalyst particles, reduces the quantity of exothermic heat which must be removed in the reactor |00 itself, and minimizes contraction in volume of the reacting gas. Where necessary or desired, this volume may be maintained in the upper portions of the reactor by introducing additional quantities of tail gas or diluent gas below one or more of the perforated plates |02 in quantity sufficient to maintain the space velocity throughout the reaction at such values as to give proper iuidization of catalyst. Heat of reaction is at least partly removed by heat exchange means of any suitable type (not shown) in reactor |00. It has been found that introduction of feed gas at a temperature considerably below the reaction temperaturen is undesirable, and accordingly it is preferable to introduce gas through conduit |011 preheated to approximately reaction temperature, and rely on heat exchange coils embedded in the masses of fluidized catalyst for removal of heat of reaction. Catalyst introduced into each of uidized beds |83 as described hereinafter may also be cooled prior to such introduction in order to take up part of the heat of reaction. Preferably a substantially constant temperature is maintained throughout the reactor.

The catalyst slowly becomes deactivated during use. This deactivation is caused by several factors, those which are believed at the present time to be of most importance being the accumulation of wax on the particles and the formation of carbon on the surface of and/or in admixture with catalyst particles. Catalyst is withdrawn from the bottom of reactor |00 and passed via conduit |01 into the top of reactivator iti. A transport gas, preferably one rich in hydrogen, enters conduit |01 from line |08 at sufficient velocity to lift the catalyst particles through line |01 and carry them into the reactivator |0|. The rate of catalyst withdrawal from the reactor |0 is such that the catalyst passed to the reactivator |0| has lost a con siderable amount of its initial activity. Ordinarily however, this catalyst still has some activity for the synthesis reaction. The catalyst enters the uppermost fluidized bed |03 in reactivator |3|, and the particles in that bed overflow through one of the downcomers |09 into the next lower fiuidized bed |0|. This in turn overflows through its downcomer into the bed below, and so on until the iiuidized bed in the bottom of reactivator |0| is reached. Into the bottom, which is preferably cone shaped as shown, the reactivation gas is introduced from line ||0. This gas is ordinarily hydrogen of fairly high purity, for example a hydrogen-methane mixture containing at least 50 per cent hydrogen or a hydrogen-steam mixture containing not more than 5 per cent steam, which has been preheated to temperatures of the order of 600 to 900 F. The reactivation gas, which also acts as a iiuidizing gas, flows through the bed maintained at the bottom of reactivator |0| and upwardly through each of the fiuidized beds |03 and finally out cyclone separator or separators and conduit ||2.

In accordance with my invention reactivator |0| is operated in a particular Way so as to give the most efficient utilization of reactivation gas while at the same time supplying portions of catalyst of varying levels of activity. The catstreams.

25 alyst which is passed entirely through reactivaf tor |0| has been maintained under reactivation conditions for a maximum period of time, and has also encountered during passage through reactivator |0|, increasing concentrations of hydrogen in the reactivation gas, iinally contacting the fresh gas introduced through conduit ||0. This catalyst is withdrawn from the bottom of reactivator |0| and passed via valved line ||3 into the uppermost iiuidized bed |03 maintained in the top of reactor |00. Less active catalyst, which however has had most of its catalytic activity restored, is withdrawn from the first iiuidized bed |03 above the bed in the bottom of reactivator 0| and passed via valved liine I4 into the next to the top iiuidized catalyst bed |03 maintained in reactor |00. Similarly, catalyst of an intermediate stage of activity is withdrawn from the next higher bed in reactivator 0| and passed via valved line |5 into the next lower bed in reactor |00. In like manner, valved lines H0 and ||1 are employed to withdraw less active catalyst from the next to the top bed |03 in reactivator |0| and introduce it into the next to the bottom bed |03 in reactor |00, and withdraw the least active but partially reactivated catalyst from the highest luidized bed in reactivator 0| and introduce it into the bottom bed of reactor |00.

The reactivation gas is most efficiently used by the procedure described, since it rst contacts in the bottom of reactivator i0! the most nearly reactivated catalyst which needs the highest concentration of hydrogen, and subsequently contacts catalyst which is more and more clearly deactivated but which undergoes appreciable reactivation even in the presence of the relatively dilute hydrogen in the upper portions of reacti vator |0|. The dilution of the reactivation gas is caused by liberation of hydrocarbons and other J materials from the catalyst which have been occluded on the catalyst or which have been formed during the reactivation reactions.

I prefer to introduce the reactivation gas into the bottom of reactivator 0| at the maximum desired reactivation temperature, for example 900t7 F., and allow its temperature to drop as it passes upwardly through successive iiuidized catalyst beds, leaving the topmost bed at a ternperature approximating that of the entering catalyst, say 600 F. Additional cooling in or between beds to provide this decreasing temperature gradient may be employed. However, it is preferred to adjust the relative flow rates'of gas and catalyst so as to achieve the gradient without any 'separate cooling steps.

This featurecf my invention has several advantages. There is maximum heat economy and eiciency, as it is most convenient to preheat the hydrogen-rich reactivation gas rather than the solid catalyst particles. The maximum temperature is provided where most needed, which is also the point of maximum hydrogen concentration thus giving most eicient reaction. The incoming catalyst in the top bed of reactivation |0| is subjected to the lowest reactivation temperature which avoids too fast an action but which is quite adequate to effect the iirst removal of occluded material from the catalyst, probably more by volatilization than by chemical action. As the catalyst passes downwardly it encounters the increased temperatures and hydrogen concentrations required for the succeeding stages of reactivation. Another advantage useful when catalystis not `being cooled Aprior to reintroduction into reactorill is that the hottest catalyst enters the top of the reactor where its higher temperature is not nearly so objectionable as it would be in lower parts of the reactor where the concentration of reactants is higher.

Flow of catalyst through reactor |00 is similar to that described above in reactivator 0| in that each iluidized bed of catalyst overilows into the next lower bed through a downcomer |09. The synthesis gas entering the bottom of reactor |00 via line l 0A iirst encounters the least active catalyst in the system. This avoids too complete a reaction in the first portions of the reactor. As the reaction mixture flows upwardly through the reactor |00 it encounters iudized beds containing more and more active catalyst. The last or uppermost bed through which the reaction mixture flows is the only one in which the completely reactivated catalyst from the bottom of reactivator |0| is encountered. By maintaining the highest level of activity in the uppermost fluidized bed, the conversion of carbon monoxide can be driven to completion without unduly extended contact times. If all of the catalyst were reactivated to the same level and introduced into the top part and then allowed to flow downwardly through the reactor, the synthesis reaction in the lower portion of the reactor would be unduly slowed down by virtue of the relative uniformity of catalyst activity for all particles of the catalyst mass. By operating as described, catalyst which has just undergone some reactivation is made available in each bed of the reactor. This admixing of catalyst reactivated to an extent chosen in accordance with the location in the reactor, and catalyst which has passed downwardly from upper portions of the reactor, provides the most eliicient catalyst mixture for the reaction at each level in the reactor. The exact mechanism of reactivation is not fully understood, but the catalyst withdrawn from intermediate points in reactivator |0| is believed relatively free of highly active particles of a nature of those passed from the bottom of reactivator |0| via line ||3 to the top-most tray of reactor |00. Thus the method of operating described is yalso superior to one in which simple mixtures of unreactivated and completely reactivated catalyst are used for introduction at various levels in the reactor. Highly active catalyst, either new or prepared by a relatively complete reactivation, give very undesirable results when contacted with fresh synthesis gas, producing excessive amounts of light gases on the one hand and heavy tars or carbonaceous materials on the other hand, the catalyst itself becoming too rapidly deactivated and undergoing a certain amount of permanent impairment of activity. Further advantages of my procedure will thus be seen. The most active catalyst encounters only a highly diluted synthesis gas in the upper portions of reactor |00, and the relatively high activity of this catalyst is needed in order to effect theA nal stages of conversion while minimizing the undesirable effects on reactants and catalyst just described.

A certain amount of catalyst becomes permanently lost to the system as nes or otherwise, and fresh make-up catalyst must therefore be introduced. This introduction is ordinarily made in a batchwise manner, since the new catalyst is best prepared in relatively small batches and introduced into the system fairly soon after its reduction from the oxide to the active metal form. l prefer not to prepare large quantities of the active catalyst for storage. since this is a pyrophoric material and very dangerous to store. The make-up catalyst is introduced, as described, via line ||8y only into the upper bed or beds of reactor I via valved lines ||3 and/or |I4. I sometimes prefer to introduce make-up catalyst in the oxide form, thus allowing reduction in situ in reactor during the conversion, and avoiding the necessary equipment and operation required for separate reduction and the necessity of storing reduced catalyst. By proper control of the relative quantities of make-up iron oxide promoted with the usual promoters and active catalyst, the over-all composition of catalyst in the uppermost beds of reactor Hill immediately after the make-up iron oxide has been introduced thereinto can be maintained at a value equivalent to catalyst which is between 80 and 90 per cent reduced. Operation with a catalyst mixture containing iron oxide which mixture is less than 80 per cent, or more than 9U per cent, reduced to the metallic form is in this way avoided, thus preventing the undesirable eiects which are disclosed in the copending application of John Paul Hogan, Serial No. 100,139, filed June 20, 1949. The final reduction is gradually effected in situ, so the over-active eiects of new completely reduced make-up catalyst are not encountered.

As an alternative, I may introduce make-up unreduced iron oxide in admixture with promotors into the reactivation zone |BI (by means not shown) and effect its reduction to active catalyst from therein. This introduction is best made into the bottom one or two beds in zone l0 I, in order to take advantage of the higher temperatures l normally maintain in those beds; the presence of some not completely reduced make-up catalyst in the catalyst streams passed to the reactor through lines I3 and He is also advantageous in modifying the over-all activity of those streams.

While the relative quantities of catalyst in the various parts of reactor ISU and/or reactivator |0| can be varied, I prefer that the quantity in each bed in reactor |00 be essentially equal. Similarly the various beds in reactivator |0| are also preferably equal in volume to each other. It will be clear that the quantity of catalyst passing through the downcomers |09 in reactor |60 will be progressively greater in the downcomers nearer the bottom of the reactor since they must carry the overflow from higher beds as well as material introduced into the particular bed itself; however, beds of equal volume are ordinarily controlled by the height of the top of the downcomer above the perforated plate. Similarly, in reactivator the downcomers will carry a smaller and smaller volume as the bottom of the reactivator is approached since catalyst is being Withdrawn from each bed for passage to the reactor. A certain amount of catalyst will be carried over from one bed to the next higher bed by suspension in the upwardly flowing gases. Ordinarily, the quantity so carried over will not be suiiiciently great to throw the system out of balance as sufcient space is provided above the level of each fluidized bed to allow reasonably satisfactory disengagement of suspended particles from the gases. However, any suitable means may be provided between the beds for further minimizing catalyst carry-over if desired.

In the method of eiecting the Fischer-Tropsch synthesis described and shown in Figure 4, the temperature is preferably maintained constant by heat exchange, and the depressing effect on the reaction rate normally caused by the decrease in concentration of reactants in the direction of 28' flow thereof is at least partially and preferably completely overcome and compensated for by the increasing catalytic activity provided in the direction of flow of reactants. Various advantages thus obtained are similar to those described earlier in this application.

Another related process in which various features of my invention may be employed to good advantage is that known as the Oxo process. In this process unsaturated organic compounds, usually olenic compounds, are reacted with a mixture of hydrogen and carbon monoxide, preferably having a H2:CO ratio of about 1:1, at high pressures of the order of G-3000 p. s. i. and in liquid phase. Suitable temperatures vary with reactants and products desired but are generally in the range of Z50-300 F. for the rst stage and somewhat higher say 350 for the second stage. A cobalt catalyst is ordinarily used, though others, especially iron, are sometimes applicable. The various modes of operation described herein may be applied to this process with suitable modification which will be apparent from consideration of the present disclosure. The procedure described above with respect to Figure 3 is particularly suitable. When impure heavy oleflns are used as reactants in the Oxo process, my invention provides great advantage in giving clean catalyst surfaces throughout the reaction zone by virtue of the multipoint introduction of the catalyst. Products of the reaction are largely aldehydes and alcohols, with perhaps some ketones, in the rst stage, and are usually subjected to hydrogenation in a second stage for more complete conversion into alcohols. In one preferred modification, I introduce hydrogen multipoint into at least the latter portions of the reaction zone in order to increase the H21CO ratio. By this means aldehydes formed in the rst portion of the reactor are further hydrogenated to alcohols in the latter portions of the reactor, so that alcohols, which are ordinarily preferred, are obtained directly in a once-through operation. This operation is illustrated in Figure 5 wherein a reactor |3 of any suitable type for carrying out the Oxo process has introduced into it at one end olen reactant from line |32 and hydrogen plus carbon monoxide reactants from line |34. Catalyst from line |36 is introduced into reactor |30 at a plurality of points via lines |38, |40, |42, |44 and lli which are exemplary of any desired number of such lines, while a hydrogen-rich gas from line lli is introduced multipoint into the latter portions of the reaction zone as through lines |58, |52 and |55. Total reaction mixture, including alcohols formed as described above, issues from reactor |30 via line |56. One desirable operation involves multipoint addition of hydrogenation catalyst to the second stage. This catalyst can be dierent from, and preferably readily separable from by virtue of particle size or otherwise, the catalyst used for the initial reaction between olens and the Hz-CO gas. For instance nickel, or copper chromate, may be used. They are not subject to much carbonyl formation under the given conditions as is the cobalt catalyst, hence a removal of CO between stages, which is a common feature of conventional operations, is obviated.

Various modes of operating have been disclosed herein, along with the broad concepts involved, so that one skilled in the art may, by suitable simple modifications, apply the principles of my invention to conform to the economic and practical considerations which will vary somewhat with each particular material treated. By following the teachings of my invention, the contacting of catalysts with reactants may be so exactly correlated with reaction conditions as to give a well regulated operation not heretofore taught. While I have disclosed certain specific processes, with particular reference to petroleum conversions, I do not wish to be limited to the exact modications described, but only by the appended claims.

I claim:

1. A method of synthesizing aliphatic organic compounds by reaction oi' hydrogen with carbon monoxide, which comprises passing a gas comprising hydrogen and carbon monoxide upwardly through severai individual nuidized beds of powdered synthesis catalyst maintained one above the other in a reaction zone maintained at synthesis conditions, introducing reactivated catalyst into the uppermost of said beds, introducing catalyst reactivated to a lesser extent into the next lower of said beds, and introducing into each of the remainder of said beds catalyst activated to successively lesser extents, the least activated catalyst being introduced into the lowermost of said beds, flowing catalyst downwardly through said several beds to maintain a nxed height of catalyst in each bed, withdrawing catalyst at least partially deactivated from the lowermost of said beds and passing same into the topmost of several individual superimposed fiuidized beds in a reactivation zone, passing reactivation gas upwardly through said beds in said reactivation Zone under conditions effecting reactivation I said catalyst for said synthesis reaction, passing catalyst downwardly through said several beds in said reactivation zone and withdrawing the aforesaid most reactivated catalyst from the bottom thereoil for passage to the uppermost catalyst bed in said synthesis reaction zone, as described, and withdrawing catalyst from each of said beds in the reactivation zone for introduction into the successive beds of said reaction Zone, the more reactivated catalyst withdrawn from lower beds in said reactivation zone being introduced into the upper beds of said reaction zone and the less reactivated catalyst withdrawn from higher beds of said reactivation zone being introduced into successively lower catalyst beds in said reaction zone as described, whereby synthesis reaction mixture passing upwardly through said reaction zone encounters successively more catalyst activity in the direction of how.

2. A method according to claim 1 wherein an essentially constant temperature is maintained throughout said synthesis reaction zone, and the quantity and activity of catalyst introduced into each of said catalyst beds .in said synthesis reaction zone is separately controlled to provide an essentially constant rate of reaction throughout said zone despite the decreasing concentration of reactants in the direction of flow of synthesis gas.

3. A method according to claim 1 wherein a reduced iron oxide synthesis catalyst is employed.

4. A method according to claim 1 wherein a metallic synthesis catalyst and a hydrogen-rich reactivation gas are employed, said reactivation gas is introduced into the bottom of said reactivation zone at a maximum reactivation temperature, and a decreasing temperature gradient is maintained in the direction of flow thereof through said zone.

5. A method according to claim 1 wherein fresh make-up catalyst is introduced into the system only into at least one of the two uppermost i'luidized beds of catalyst in said synthesis reaction zone.

6. A method according to claim 5 wherein fresh make-up catalyst is introduced intermittently in the form of unreduced iron oxide, and in such quantities that the composition of the bed into which same is introduced corresponds, immedi ately after said introduction, to catalyst from to per cent reduced to the metallic form.

7. An improved method of reactivating metallic synthesis catalyst employed for the synthesis of aliphatic organic compounds by reaction of hydrogen with carbon monoxide which comprises maintaining a plurality of individual luidized beds of catalyst superimposed one above the other in a reactivation zone, passing hydrogen rich reactivation gas upwardly through said individual beds from the bottom to the top of said reactivation zone at conditions eiecting reactivation of said catalyst for said synthesis reaction, introducing catalyst to be reactivated into the topmost of said beds, flowing catalyst downwardly into each bed from the next higher bed to maintain a constant catalyst level in each bed, providing suicient residence time of catalyst within each bed to effect some reactivation thereof and such that catalyst withdrawn from the lowermost bed is the most active, and withdrawing catalyst from a plurality of said beds each portion of withdrawn catalyst being reactivated to a diiierent extent for introduction into a synthesis reaction.

8. A method according to claim 7 wherein a decreasing temperature gradient is maintained in the direction of ilow of reactivation gas whereby catalyst entering the top of said reactivation zone progressively encounters higher temperatures and higher hydrogen concentrations as it passes downwardly through the successive beds in said zone.

9. In the reaction of organic compounds containing olefinic unsaturation with carbon monoxide and hydrogen to form at least one material selected from the group consisting of aldehydes and alcohols, the improvement which comprises effecting said reaction in the presence of a mobile catalyst for the reaction, introducing said catalyst into the reaction zone at a plurality of points for flow through said zone, and introducing a hydrogen-rich gas into said reaction zone at a plurality of points past the point of introduction of reactants thereinto in such quantities as to provide sufiicient hydrogen to effect conversion of aldehydes to alcohols in the latter portion of the reaction zone.

THOMAS B. HUDSON.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF SYNTHESIZING ALIPHATIC ORGANIC COMPOUNDS BY REACTION OF HYDROGEN WITH CARBON MONOXIDE, WHICH COMPRISES PASSING A GAS COMPRISING HYDROGEN AND CARBON MONOXIDE UPWARDLY THROUGH SEVERAL INDIVIDUAL FLUIDIZED BEDS OF POWDERED SYNTHESIS CATALYST MAINTAINED ONE ABOVE THE OTHER IN A REACTION ZONE MAINTAINED AT SYNTHESIS CONDITIONS, INTRODUCING REACTIVATED CATALYST INTO THE UPPERMOST OF SAID BEST, INTRODUCING CATALYST REACTIVATED TO A LESSER EXTENT INTO THE NEXT LOWER OF SAID BEDS, AND INTRODUCING INTO EACH OF THE REMAINDER OF SAID BEDS CATALYST ACTIVATED TO SUCCESSIVELY LESSER EXTENTS, THE LEAST ACTIVATED CATALYST BEING INTRODUCED INTO THE LOWERMOST OF SAID BEDS, FLOWING CATALYST DOWNWARDLY THROUGH SAID SEVERAL BEDS TO MAINTAIN A FIXED HEIGHT OF CATALYST IN EACH BED, WITHDRAWING CATALYST AT LEAST PARTIALLY DEACTIVATED FROM THE LOWERMOST OF SAID BEDS AND PASSING SAME INTO THE TOPMOST OF SEVERAL INDIVIDUAL SUPERIMPOSED FLUIDIZED BEDS IN A REACTIVATION ZONE, PASSING REACTIVATION GAS UPWARDLY THROUGH SAID BEDS IN SAID REACTIVATION 